Exhibit 99.1 DIANTHUS THERAPEUTICS HIGHLIGHTS RECENT BUSINESS ACHIEVEMENTS AND REPORTS Q1 2026 FINANCIAL RESULTS Early GO decision reached in CAPTIVATE in March 2026 based on GO criteria of 20 confirmed responders achieved with less than 40 planned participants completing open-label Part A Claseprubart granted Orphan Drug Designation by FDA for Myasthenia Gravis Phase 3 registrational trial of claseprubart evaluating 300mg/2mL Q2W and 300mg/2mL Q4W in generalized Myasthenia Gravis (gMG) on track to initiate ...